1. Field of the Disclosure
This disclosure relates generally to drilling system that include a drilling assembly that include a mud pulse telemetry system in a drilling assembly for transmitting signals between downhole locations and a surface location during drilling of wellbores.
2. Background of the Art
Wells (also referred to as wellbores or boreholes) are formed in earth formations for the production of hydrocarbons (oil and gas). A drill string including a drilling assembly (also referred to as a bottomhole assembly or “BHA”) attached to a drill pipe is conveyed into the wellbore for drilling a wellbore. A drill bit connected to the end of the drilling assembly is rotated by rotating the drill pipe and/or by a motor in the drilling assembly to form the wellbore. A fluid (referred to as “mud”) is supplied under pressure into the drill string, which fluid discharges at the bottom of the drill bit and returns to the surface along with rock cuttings cut by the drill bit. The drill string commonly includes a number of sensors, including a pressure sensor, vibration sensor, temperature sensor, accelerometers, gyroscopes, etc. and also tools referred to a logging-while-drilling tools that may include resistivity, acoustic and nuclear sensors for proving information or characteristics of the formations through which the wellbore is being drilled. The data obtained from such sensors and tools is processed in the drilling assembly to obtain certain parameters and some such information is transmitted during drilling to a surface computer system for further processing and to control the drilling operation. Mud pulse telemetry in which a pulsing device (also referred to as a “pulser”) generates pressure pulses in the fluid passing through the drilling assembly is commonly used to transmit signals from the drilling assembly to the surface. The data or information is transmitted as coded pressure pulses, which are decoded by the surface computer. During drilling, a typical mud pulser substantially continuously generates pressure pulses over long time periods, often several days. In addition, a number of wellbores are currently drilled in formations having temperatures above 300 degrees Fahrenheit. A majority of currently utilized mud pulsers include oil fillings, elastomers and/or electrical high pressure connectors, which tend to deteriorate over time and are not suitable for use in high temperature wells.
The disclosure herein provides pulsers that are suitable for high temperature use and also may be made without the use of oil fillings, elastomers or electrical high pressure connectors.